Electronic products, such as notebook computers, cellular phones, personal digital assistant (PDA) devices and digital music players (for example, Apple iPod and MP3 player) are now made compact for portability. Besides mobile communication services and data/information storage, these portable electronic devices also provide entertainment for general consumers. These devices usually have built-in chargeable batteries and when the batteries run out of power, recharge can be done by electrically connecting a power-supplying device, often particularly designed for the specific portable electronic device, to an external power source, such as an alternating current (AC) power sources, for example a 110V/220V wall outlet, or a direct current (DC) power source, for example a vehicle cigarette lighter adaptor, which is usually of 12V DC.
However, the conventional power-supplying devices are usually designed for specific electronic devices and only supply power to and charge the specific portable electronic device. In other words, hardware interface and output voltage of each type of built-in rechargeable battery can only adapt to a specific electronic product. If a user owns several portable electronic devices, each requiring different input voltage or current, the user has to buy several power-supplying devices for the different portable electronic devices. Thus, the user not only has to spend more money to purchase different power-supplying devices, but also has to carry all these power-supplying devices for charging the electronic devices that are carried with him or her.
Therefore, it is desired to provide a power-supplying device that detects voltage or current required by a connected electronic device and accordingly adjusts the power output to the electronic device, whereby the power-supplying device fits for a variety of different portable electronic devices and provide variable output voltages for these different portable electronic devices, and consequently, supplying adequate powers to different portable electronic devices or charging rechargeable batteries of different specifications can be done with a single power-supplying device.